Abrasive article



Patented Sept. 5, 1922.

name

@NHTED STATES PATENT @FFIQE.

HENRY ROBERT POWER, OF NIAGARA FALLS, NEW YORK, ASSIGNOR TO THE CARBO- BUNDUM COMEANY, OF NIAGARA FALLS, YORK, A CORPORATION OF PENN- SYLVANIA.

No Drawing.

To all whom it may concern:

Be it known that I, HENRY ROBERT POWER, a citizen of the United States, residing at Niagara Falls, in the county of Niagara and State of New York, have invented a new and useful Improvement in Abrasive Articles, of which the following is a full, clear, and exact description.

The invention relates to abrasive articles such as grinding wheels and the like, and

more especially to such abrasive articles containing a resinous bond.

In making abrasive articles such as abrasive wheels of this character, abrasive grains or particles such as silicon carbide, or aluminous abrasives such as emery, aloxite or corundum are held together by a bond containing shellac. In some such compositions the abrasive grains are mixed with powdered shellac, with or without the addition of powdered rosin, and compounding chemicals. and fillers. This mixture is warmed sufficiently to mold into shape, and afterwards is baked to convert the shellac into a hard elastic bond which holds the abrasive grains securely in place. During the baking process the rosin reacts chemically with the compounding chemicals to form resinates which also have certain bonding properties. When rosin is used in such abrasive mixtures, a

chemically equivalent amount of a metallic oxide, such as zinc oxide, lead oxide or lime,

is required to react with the rosin to form a resinate, the melting point of which is higher than the original rosin. For example, rosin employed in compounding abrasive mixtures melts at about 60 centigrade, whereas the zinc, lead or calcium resinates or driers melt at a temperature cc of from 115 to 145 centigrade.

As a substitute for such rosin or resinates I use a resinous coal-tar distillate. This resinous distillate is preferably a polymerized compound of the coumarone indene roup. In making abrasive compositions I ave used a com ound of this character known commercially as cumar, a mixture of polymerized benzofuran or paracoumarone and paraindene. This is obtained from the distillation of coal-tar. When coaltar is distilled, one of the distillates is known as light oil, which on distillation yields among other things heavy naphtha. This in turn yields on distillation compounds of the coumarone-indene group, such as coum- Application filed November 17, 1919. Serial No. 338,604.

arone and indene, these substances being unpolymerized or polymerized depending upon the temperature control of the process. If uncontrolled, the process yields polymerized products. If the process is properly controlled the products are substantially unpolymerized and may be later put through a polymerizing process which yields as the ultimate product the polymerized products such as paracoumarone and paraindene. The substance known commercially as cumar is a mixture containing paracoumarone and paraindene. The substances, however, may be used alone. For example, substantially pure paracoumarone of the proper grade may be used in place of the commercial mixture.

The term coumarone resin, as used herein, is therefore intended to include not only substantially pure paracoumarone, but also the resins known commercially as coumarone resins which contain other polymerizable compounds of the coumarone-indene group. In my Patent, No. 1,310,292, granted July 15, 1919, for abrasive wheel, I have more fully defined the organic com pounds referred to and given the structural formulae therefor.

There are several commercial grades of cumar or paracoumarone, some being highly refined and odorless, tasteless and almost odorless. Others have a characteristic light yellow to a dark brown color. The grades that are hard at ordinary temperatures are brittle. Others are tough and cold flow ng at ordinary temperatures. The melting points of the different grades vary from 0 Centigrade to 160 Centigrade. The specific gravity is about 1.1 in all grades. Qn heating, it melts, giving a pleasant sweetish odor and on cooling again is found to have lost none of its former chemical and physlcal properties. It is practically inert; it has no saponification number, no acid number; it is insoluble in alcohol and dissolves readily in solvent naphtha. With an alkali it yields no lather. Furthermore, it oxidizes very slowly, even in the presence of strong ox1d1zing agents like nitric acid.

The use of the above described compound or compounds of the coumarone-indene group has distinct advantages in the manufacture of abrasive articles, particularly those in which a shellac or similar elastic binder is used.

When used as a substitute for the resin ates or so-cailed driers, the higher melting grades of cumar or paracoumarone, such as those having the melting point at about 160 centigrade, are employed. The cumar thus used requires no equivalent amount of metallic oxide as does rosin, for it melts at a temperature equal to that of the substituted resinate. Furthermore, cumar is a neutral substance and if it is used together with some rosin, it will not react with the basic oxides present in the abrasive mixture. The cumar can be used either as a complete substitute for rosin and metallic oxides or it may be used with them. It permits a saving in the amounts of both the metallic oxide and rosin or metallic oxide alone.

Such a substitution also permits of a larger percentage of abrasive grains in the mix, to the extent of the amount of metallic oxide eliminated from the mix by substituting its equivalent chemically in rosin with the cumar or paracoumarone. Therefore, this gives compositions of different grades than are possible when the rosin-oxide mixes are used. On the other hand, if a lower abrasive grain content is desired, metallic oxide fillers may be used in place of the abrasive grains without influencing the bonding properties of the binder because the cumar or paracoumarone remains inactive with respect to the basic oxides.

In addition-to this use of cumar or paracoumarone which results in economy and flexibility in the mixes, there is the difference in character of the bond produced with shellac and cumar as compared with shellac and rosin-oxide compositions. Cumar or paracoumarone is decidedly brittle and gives a quick wearing composition which continually exposes fresh surfaces of abrasive grains. It is not likely, therefore, to glaze or become filled with particles of the material abraded.

In making abrasive articles such as abrasive wheels, I mix the abrasive grains together with powdered shellac and the powdered cumar or paracoumarone, with or without powdered rosin and basic materials and fillers, and mold the mix either cold or warm into the desired shape. The shaped article is then baked at a temperature sufficiently high to cause the bond to flow and hold together the abrasive grains, the particular temperature used for baking depending upon the composition of the mix.

While l have specifically described the preferred embodiment of my invention, it is to be understood that the invention isnot to be limited to all of the details hereinbefore described, but may be otherwise embodied within the scope of the following claims.

I claim:

1. An abrasive article comprising abrasive particles and a binder containing shellac and coumarone resin.

2. An abrasive article comprising abrasive particles and a binder containing shellac, rosin and coumarone resin.

3. An abrasive article comprising abrasive particles and a binder containing coumarone resin.

4. An abrasive articie comprising abrasive' particles and a binder containing a polymerized resinous coal-tar distillate.

5. An abrasive article comprising abrasive particles and a binder containing a resinous coal-tar distillate.

In testimony whereof, I have hereunto set my hand.

HENRY ROBERT POWER. 

